rtc: ds1307: add trickle charger support

Some DS13XX devices have "trickle chargers".  Its configuration register
is at different locations, the setup is the same, though.  Since the
configuration is board specific, introduce a platform_data to this driver.
Tested with a DS1339 on a custom board.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Alessandro Zummo <alessandro.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/rtc/ds1307.h b/include/linux/rtc/ds1307.h
new file mode 100644
index 0000000..291b1c4
--- /dev/null
+++ b/include/linux/rtc/ds1307.h
@@ -0,0 +1,22 @@
+/*
+ * ds1307.h - platform_data for the ds1307 (and variants) rtc driver
+ * (C) Copyright 2012 by Wolfram Sang, Pengutronix e.K.
+ * same license as the driver
+ */
+
+#ifndef _LINUX_DS1307_H
+#define _LINUX_DS1307_H
+
+#include <linux/types.h>
+
+#define DS1307_TRICKLE_CHARGER_250_OHM	0x01
+#define DS1307_TRICKLE_CHARGER_2K_OHM	0x02
+#define DS1307_TRICKLE_CHARGER_4K_OHM	0x03
+#define DS1307_TRICKLE_CHARGER_NO_DIODE	0x04
+#define DS1307_TRICKLE_CHARGER_DIODE	0x08
+
+struct ds1307_platform_data {
+	u8 trickle_charger_setup;
+};
+
+#endif /* _LINUX_DS1307_H */